From 00064177f9bae914c89799c25d05ba0774cdbf31 Mon Sep 17 00:00:00 2001
From: joachimschmidt557 <joachim.schmidt557@outlook.com>
Date: Tue, 22 Oct 2019 19:06:32 +0200
Subject: [PATCH] add matrix

---
 matrix.zig | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 matrix.zig

diff --git a/matrix.zig b/matrix.zig
new file mode 100644
index 0000000..085b5b0
--- /dev/null
+++ b/matrix.zig
@@ -0,0 +1,93 @@
+const std = @import("std");
+
+fn Matrix(comptime T:type) type {
+    return struct {
+        alloc: ?*std.mem.Allocator,
+        data: []T,
+        width: usize,
+        height: usize,
+
+        const Self = @This();
+
+        pub fn init(allocator: *std.mem.Allocator, w: usize, h: usize) !Self {
+            return Self {
+                .alloc = allocator,
+                .data = try allocator.alloc(T, w * h),
+                .width = w,
+                .height = h,
+            };
+        }
+
+        pub fn deinit(self: *Self) void {
+            if (self.alloc) |allocator| {
+                allocator.free(self.data);
+            }
+        }
+
+        pub fn fromSlice(slice: []T, w: usize) Self {
+            return Self {
+                .alloc = null,
+                .data = slice,
+                .width = w,
+                .height = slice.len / w,
+            };
+        }
+
+        pub fn get(self: *Self, x: usize, y: usize) T {
+            return self.data[x*self.width + y];
+        }
+
+        pub fn set(self: *Self, x: usize, y: usize, item: T) void {
+            self.data[x*self.width + y] = item;
+        }
+    };
+}
+
+fn mul(alloc: *std.mem.Allocator, a: *Matrix(i32), b: *Matrix(i32)) !Matrix(i32) {
+    var result = try Matrix(i32).init(alloc, b.width, a.height);
+
+    var i: usize = 0;
+    while (i < a.height) : (i += 1) {
+        var j: usize = 0;
+        while (j < b.width) : (j += 1) {
+            result.set(i, j, 0);
+
+            var k: usize = 0;
+            while (k < a.width) : (k += 1) {
+                result.set(i, j, result.get(i, j) + a.get(i, k) * b.get(k, j));
+            }
+        }
+    }
+
+    return result;
+}
+
+fn print(a: *Matrix(i32)) void {
+    var i: usize = 0;
+    while (i < a.height) : (i += 1) {
+        var j: usize = 0;
+        while (j < a.width) : (j += 1) {
+            std.debug.warn("{} ", a.get(i, j));
+        }
+        std.debug.warn("\n");
+    }
+}
+
+pub fn main() !void {
+    const arena = &std.heap.ArenaAllocator.init(std.heap.direct_allocator);
+    defer arena.deinit();
+
+    const allocator = &arena.allocator;
+
+    var a_data = [_]i32{ 1, 2, 3, 4 };
+    var a = Matrix(i32).fromSlice(a_data[0..], 2);
+
+    var b_data = [_]i32{ 2, 5, 6, 7 };
+    var b = Matrix(i32).fromSlice(b_data[0..], 2);
+
+    var c = try mul(allocator, &a, &b);
+
+    print(&a);
+    print(&b);
+    print(&c);
+}